Ultimate Fudge Brownies

Bahan-bahan (16 porsi)

• 4 ounces 70% cacao dark chocolate, (chopped)
• 2 teaspoons espresso powder
• 6 tablespoons unsweetened natural or Dutch process cocoa powder, (divided)
• 1 cup unsalted butter
• ¾ cup granulated white sugar
• ½ cup packed dark brown sugar
• 2 teaspoons vanilla extract
• 1 teaspoon kosher salt
• 3 large eggs
• ½ cup all purpose flour
• flaky sea salt, (for topping (optional))